System for determining the height of a geodetic tool

ABSTRACT

The invention relates to a system for determining the height of a tripod-mounted geodetic tool using a reference area. Said system comprises a spacer element ( 20 ) to be mounted on the tripod ( 25 ) and means ( 2 ) for linear measurement which are to be applied on the spacer element ( 20 ). A scale is disposed on the means ( 2 ) in such a manner as to directly indicate the height (h) of the tool ( 28 ). The means are preferably configured as a tape measure ( 2 ) or a plumb bar ( 1 ′). The invention provides a means for measuring the height of the tool outside the plumb line ( 32 ) with a sufficient amount of exactness and without substantial additional costs and/or effort.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a system for determining the height of atripod-mounted geodetic tool above a reference area-to a spacer and adistance measuring device for such a system.

2. Description of the Related Art

For surveying tasks using geodetic tools, it is necessary to know, forexample, the height of the optical axis of the tool above a referencearea. The reference area is defined by a geodetic point of reference(reference point) which is marked, for example in a boundary stone.

In DE 40 07 245 A1, a laser apparatus mounted on a tribrach prior toassembly and intended for perpendicular positioning above the referencepoint is used. The height of the device above the reference point isthen to be determined using the laser. Reference points are, forexample, generally marked in a boundary stone by indentations ornotches. The reference plane is however defined by the maximumprojection of the boundary stone. The measurement by means of a laserbeam is therefore inaccurate.

Other systems use measuring tapes in the form of roll-type tapemeasures. The roll-type tape measure is fastened to an adapter (heightmeasuring bracket, height hook) so that it is present in the plumb lineabove the reference point during the measurement. Known adapters arefastened by means of a spindle in a centering bush of the tool and runaround the tripod and the tripod head into the plumb line. An operatorpulls the tape measure out of the roll-type tape measure and runs it tothe boundary stone. The height of the tool is indicated on a mark on theroll-type tape measure. The measuring procedure is difficult andsusceptible to inaccuracies because, on the one hand, the end of theroll-type tape measure has to be held by the user on the boundary stoneand, on the other hand, the mark has to be read at a height.Wind-related inaccuracies may also occur. Such adapters consist of metaland are relatively bulky. This make them problematic to transport.

U.S. Pat. No. 5,720,106 describes a measurement of the slope height of atripod-mounted geodetic tool above the reference area outside the plumbline. Here, however, it is the uncorrected slope height that isindicated on the mark to be read on the roll-type tape measure. The trueheight of the geodetic tool above the reference area can be calculatedbased on the slope height and the on the geometrical relationships ofthe tripod-mounted geodetic tool.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a system of the type statedat the outset for determining the height of a tripod-mounted geodetictool above a reference area, which system gives sufficiently accuratemeasurement using simple means.

The arrangement, according to the invention, departs from the principleof measuring inside the plumb line. Instead, the measuring distancemakes an angle with the plumb line. By a suitable design of the scale,the perpendicular height above the reference point can nevertheless beread with sufficient accuracy.

On the one hand, a roll-type tape measure which is fastened to a spacerattached to the tribrach or to the instrument, drawn downward and placedagainst the reference area relative to the point of reference issuitable for the length measurement. The scale on the graduated tape ofthe roll-type tape measure is adapted and shows not, for example, thelength of the measured distance but directly the required perpendicularheight of the tool above the point of reference. Alternatively, it ispossible to use a measuring stick, for example a plumb bar, which isplaced on the reference area in the vicinity of the reference point andis to be read at the spacer. The scale mounted on the plumb bar in turnindicates the perpendicular height. The spacer has relatively smallexternal dimensions compared with known adapters, while roll-type tapemeasure and plumb bar are in any case carried by the user of thegeodetic tool in the standard equipment.

The scale of the roll-type tape measure or plumb bar has nonlineardivisions and—provided that the spacer is aligned horizontally—iscalculated using Pythagoras' law, which relates the lengths of the sidesof a right-angled triangle to one another. The catheti of theright-angled triangle are formed by the distance from the point ofengagement or end of the spacer to the plumb line and the height of thisspacer plane above the reference area at the reference point along theplumb line. The hypotenuse of the right-angled triangle is given by thedistance between the reference area at the reference point and the endof the spacer. If it is not intended to arrange the spacer horizontallyon the tool, the scale of the measuring device coordinated with thespacer, whether roll-type tape measure or plumb bar, is calculated in acorrespondingly different manner. What is advantageous is that it is notnecessary for the measuring spindle, the measuring blade or a stop ofthe roll-type tape measure or an end of the plumb bar to be placeddirectly on the reference point on which the plumb line stands, but canbe positioned slightly outside. The resulting inaccuracy of themeasurement can be neglected. Rather, the roll-type tape measure or theplumb bar can now be placed on the highest point of the reference point,for example of the boundary stone which defines the reference plane.

If, for example, a roll-type tape measure which is also to be used formeasuring lengths other than the height of the tool is now used formeasuring the length, application of the nonlinear scale in coded formis then possible—in order to avoid uncertainties in reading. This isalso true for the use of an inch rule.

In the context of the present invention, “coded representation” of ascale is intended to mean representations which can be read not directlybut only indirectly, whether, for example, by interspersing a mirror (inwhich case the scale representation is mounted as a mirror image on thescale support), whether via special color filter (in which case thescale representation is in false colors and cannot be differentiatedwith the naked eye) or whether by interspersing an anamorphotic lens (inwhich case the scale is mounted with distortion and defocusing). Theabove examples for coded representation are not definitive. Thus, forexample, the provision of reading slides or windows with staggered gridis possible which permits reading of the scale only in cooperation withan opposite grid making it difficult or impossible to read the scale onthe scale support directly.

If, for example, a scale is mounted on the scale support in the codedform described above, it can be read only using the correspondingreading means. If the operator attempts to read this coded scale at thereading mark which is coordinated with the scale mounted in uncodedform, the error will be directly evident. Reading is difficult if notimpossible. In a corresponding manner, a reading error is avoided forthe scale mounted in uncoded form if the operator attempts to read thisscale using the reading means.

With the use of a cylindrical lens whose axis runs along the scalesupport, a compressed scale which is readable only by means of thecylindrical lens can be mounted—preferably in the middle of the scalesupport. Above and below the compressed scale, which is visible to thenaked eye only as a dotted line, in each case directly readable andoptionally further, only indirectly readable scales can be mounted. Thecompressed scale can in this case simultaneously serve as a separatingline for different scales above and below it.

Since in general only a relatively small scale region can be read usingthe reading means, measures are taken to ensure reading which is aserror-free as possible. This is achieved, for example, by speciallydesigned scales and/or the magnification of the reading region.

Thus, the scale can be modified in such a way that, even in a relativelysmall reading region, it is clearly visible in which direction of thescale the numbers are arranged in ascending order.

The housing need not be made larger in order to increase the size of thereading region. The reading region can be broadened, for example, byproviding a mirror which is inclined at an acute angle instead of at anangle of 45°. The image of the scale is thus compressed and a readingerror—due to divisions to be read as mirror images—is avoided becauseseveral numbers arranged in ascending order corresponding to the scaleof the graduated scale appear in the field of view.

Alternatively or in addition to the mirror inclined at an acute angle,it is also possible to use a concave mirror or a corresponding concaveprism in order to compress the scale. Furthermore, a scattering lens maybe present before a mirror. Although this leads to slight distortions atthe edge of the field of vision, depending on the quality of the mirroror the lens, said distortions do not adversely affect the reading.

A similar result is obtained if the running surface on which the scalesupport moves past the reading mark is not flat but curved. The scaleappears compressed and will have small distortions in the edge regions.The distance from scale support to reading mark will have to be kept assmall as possible and constant.

The scales can be mounted both on opposite sides of the scale supportand on the same side. The scales differ, for example, in havingdifferent starting points to which the graduations noted along the scalerelate. The scales can also have different linear or nonlineardependencies—based on the length to be measured. In general, theinvention can be advantageously applied when scale graduation andmarking (apart from the coded representation) of different scales arenot identical. Thus, it would be possible to use thissystem—independently of the application described here—also forangle-measuring instruments (degree or radian graduation) orvelocity-measuring instruments (kilometers or miles per hour).

The reading marks coordinated with the different scales, for example forroll-type tape measures, can be arranged at different points of thehousing. The distance between the two marks is at least sufficientlylarge that good readability is ensured and the marks can be sufficientlyclearly distinguished by the operator.

The scale mounted in coded form on the scale support is expedientlylocated —for roll-type tape measures—on the side which, when rolled upon the scale support, the scale tape roll, faces outward. The readingmeans is then fastened in the housing wall, opposite the roll.

Expediently, the scale support—for roll-type tape measures—is passedalong a running surface or over a gangway opposite the reading mark ofthe reading means. The distance between mirror and scale support remainsthe same, regardless of the drawn-out length of the scale tape. Parallaxwhen reading is thus reduced. In order practically completely to ruleout the reading error due to parallax, a reading mark is applied notonly on that side of the reading means which faces the scale support butalso on the side facing the user.

The running surface furthermore results in a constant draw-out anglebecause the scale support in any case runs over this.

The reading mark is expediently a clearly readable line marked in color.

The measuring device according to the invention permits selectivereading of the individual scale, which must be performed in a deliberatemanner, makes the reading reliable and prevents mistakes. The roll-typetape measure used in the case of the height-measuring tool according tothe invention can of course also be used quite normally in the usual wayas a roll-type tape measure without mistakes occurring in the reading.

The scale tape can be held taut by the operator. Even in a strong wind,the accuracy of measurement is thus maintained.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention is explained in more detail below with reference to theFigures shown in the drawing.

FIG. 1 shows a system for measuring the height using a roll-type tapemeasure;

FIG. 2 shows a roll-type tape measure in cross-section;

FIG. 2a shows a further design of the roll-type tape measure incross-section;

FIG. 2b shows a roll-type tape measure having in each case two scales onboth sides of the scale support, one of the two scales being a mirrorimage in each case;

FIG. 3 shows a spacer having a retaining part for fastening a hookprovided on that end of the scale support which is drawn out;

FIG. 3a shows an embodiment of the retaining part of the spacer;

FIG. 4a shows a further embodiment of the spacer in elevation;

FIG. 4b shows a plan view of the spacer shown in FIG. 4a;

FIG. 4c shows a detail of the spacer from FIG. 4, showing the retainingpart 21 for the hook 8 for the roll-type tape measure;

FIGS. 5a, 5 b show different scales which can be mounted on the scalesupport; and

FIG. 6 shows a plumb bar for holding one or more, optionally codedscales.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a conventional tripod-25, of which two legs are shown. Aconventional tribrach 27 which is horizontally aligned is attached tothe tripod plate 26 at the top of the tripod. The tribrach 27 has beenprepared for holding, for example, a tool 28. Tripod plate 26 andtribrach 27 have respective central holes 29 through which the laserbeam of a laser positioning device (not shown) or an opticalplumb isdirected in order to align the tribrach 27 perpendicularly above thereference point marked in a boundary stone 31. The horizontal alignmentof the tribrach 27 is effected by means of adjusting screws 35 whichhave caps 19 at the top of the tribrach 27.

In order to carry out measuring tasks using the tool 28, it isnecessary, for example, to know the height of its optical axis 30 abovethe reference point. The measuring system for determining this oranother desired height comprises a spacer 20 fastened to a comer of thetribrach 27 and a roll-type tape measure 2 corresponding to FIGS. 2, 2 aor FIG. 2b with a scale tape 1. The draw-out end of the scale tape 1 ishooked, at the end of a spacer 20, into a corresponding holder on theretaining part 21 of the spacer. The housing 2′ of the roll-type tapemeasure 2 is drawn downward by the operator and is placed with ameasuring spindle 10 on the reference point or in its immediatevicinity. The scale on the scale tape 1 is applied in the form of amirror image. By means of a mirror 3 (FIGS. 2, 2 b) which reflects thescale upward substantially in the draw-out direction of the scale tape1, the resulting scale value can be read laterally correctly.

The scale itself is graduated and inscribed in such a way that it doesnot indicate, for example as in the case of a conventional roll-typetape measure, the length of the distance between retaining part 21(point of engagement) on the spacer 20 and measuring spindle 10 of thehousing of the roll-type tape measure 2 but directly indicates theheight h=c+d of the optical axis 30 above the reference plane defined,for example, by a boundary stone 31. For this purpose, the scale on thescale tape 1 is converted using Pythagoras' law according to a²=b²+c².Here, a is the distance from the point of contact of the spacer 20 (withthe scale tape or an applied plumb bar according to FIG. 6) to the footof the plumb line 32 on the reference point or the reference area, b isthe horizontal distance of the end of the spacer 20 from the plumb line32 and c is the length of the plumb line 32 from the foot of the plumbline to the point of intersection of the distance b with the plumb line32. Furthermore, the constant, known height d of the optical axis 30 ofthe tool above the point of intersection of the line from the end of thespacer 20 with the plumb line 32 has been taken into account in anadditive manner. The dimensioning of the scale on the scale tape 1 iscalculated as follows:

h=d+{square root over (a²−b²)}

Of course, this formula corresponds only to a horizontal distance. Itshould be changed accordingly depending on the specific angular positionthereof.

The desired height of the geodetic tool above the foot of the verticalis thus obtained.

Instead of the roll-type tape measure 2, it is also possible to use, forexample, a plumb bar, which can be formed, for example, according toFIG. 6. The plumb bar is placed on the boundary stone 31 and heldagainst the retaining part 21 of the spacer and read there. The scalemounted on the plumb bar is then once again calculated using the aboveformula.

The spacer 20 is fastened to the already horizontal upper part of thetribrach 27, at points with the greatest distance from the plumb line.The end of the spacer 20 is directed between the top fastenings of twotripod legs so that the scale tape 1 can be easily drawn out between thetripod legs, downward in the direction of the reference point. Thereference point in the boundary stone 31 is usually characterized by anindentation. Expediently, the measuring spindle 10 on the housing of theroll-type tape measure 2 is easily positioned outside the marking on theboundary stone, preferably at that point of the boundary stone 31 whichdetermines the reference area. However, the resulting inaccuracy of themeasurement can be neglected.

The spacer 20 is preferably designed in such a way that theinstrument-specific, previously known height d is adopted in anadapter-specific manner. This makes it possible to use the sameroll-type tape measure for different versions of geodetic tools, sincethe additive height is then omitted. For tribrachs 27 and tools 28 ofdifferent makes, it is then possible to provide separate adapters ineach case.

FIG. 2 shows a roll-type tape measure 2 in cross-section by way ofexample. The scale tape 1 is drawn out of the housing 2′ of theroll-type tape measure 2 against a restoring force of a scale tape roll4. The scale present on the outside of the roll can be read by means ofa reflecting prism 3 fastened to the housing 2′. The prism has a surface3 a opposite the roll, a surface 3 b which faces the operator and asurface 3 c having reflective properties, so that light from the scaleis reflected by the side 3 c toward the operator. A reading mark 7, forexample a colored reading line, is incorporated into the side 3 a. Tokeep the parallax during reading as small as possible, the scale tape ispassed over a guide surface 5 or over a guide web, in each case arrangedopposite the reading line. The reflective surface makes an acute anglewith the draw-out direction of the scale tape. Consequently, the scaletape can be read from the top, i.e. in the draw-out direction.

As an alternative to a reflective prism, it is also possible to use aconventional mirror, which is mounted in place of the surface 3 c of theprism. The housing is then provided with an inspection window instead ofthe surface 3 a of the prism. In this version having a mirror or prism,the scale is marked as a mirror image on the scale tape 1. Confusionwith other scales on the scale tape which are not applied as a mirrorimage is therefore prevented.

The measuring spindle 10 is pointed and forms an extension of the planeof the measuring tape. It thus permits exact positioning of theroll-type tape measure on the reference area. The measuring spindle 10is preferably hinged. This enables the roll-type tape measure 2 to beused for different purposes.

The prism is arranged in such a way that the operator can read thedistance as far as possible without parallax.

It is also possible for an inspection window 11 to be arranged on thehousing instead of a mirror, as shown in FIG. 2a, via which the scale isread directly. The corresponding scale is then applied to the other sideof the tape and accordingly without lateral inversion.

FIG. 2b shows a roll-type tape measure which optionally has four scaleson both sides of the scale support, two per side. One of the two scaleson each of the two sides of the scale support is a mirror image. One ofthe scales on side 1 a is read directly at the slit 9 and the otherscale which is upside down and a mirror image is read via the mirror 12through the inspection window 13.

If, as in this case, two scales are present on the same side of thescale support, one of which is upside down and a mirror image, thispermits reading of the scale support from any desired direction sinceone of the two scales is always readable while the other upside downscale can be read using the mirror. A reading error due to confusion ofthe two scales is likewise substantially ruled out by thisrepresentation of the scales.

The scales present on side 1 b of the scale support are read using themirror 3 or using the inspection window 11.

In this case, the mirror is inclined at an angle which is more acutethan 45°. The reading area is compressed. Reading marks 7, 7′ arepresent directly above the scale tape 1 and on the user-side window 3 bin order to keep the parallax small.

Since the light path via the mirror 3 is considerably longer than thatthrough an inspection window and only light which penetrates fromoutside through the mirror to the scale support 1 can be reflected, asmall light 15, for example an incandescent bulb or a light emittingdiode, can be mounted in the region of the scale for better readabilityof the scale and is switched on and off by simple means, for example apushbutton 14 on the surface of the housing 2′. This is useful inparticular where outdoor light conditions are poor.

The electrical energy for operating the light can be provided by abattery. However, it is also possible for a battery to be charged bymeans of a small generator which is driven by the pulling out of thescale tape. It is also possible to charge a capacitor, which howeverneed not be charged exclusively by means of an electric motor but alsoelectrostatically.

Other possible variants for such roll-type tape measures have beendescribed in the Swiss Patent Application filed by the same applicant onthe same date and having the title “Messgerät, insbesondereLängenmessgerät, mit mindestens zwei Skalen” [Measuring instrument, inparticular length measuring instrument, having at least two scales] andare hereby considered to have been disclosed.

A possible embodiment of a spacer 20 is shown in perspective in FIG. 3.The spacer 20 is fastened to the already horizontal upper part of thetribrach 27, at the points with the greatest distance from the plumbline. The end of the spacer 20 is directed between the top fastenings oftwo tripod legs, as shown in FIG. 1. Present there is a cap 19 (cf. FIG.4b) for one of the adjusting screws, via which the spacer 20 is pushedin and positioned by means of a hole 24 provided in said spacer. Screws23 which permit horizontal alignment of the spacer 20, which can bechecked by means of a spirit level 22, are arranged on either side ofthat region of the spacer 20 which is coordinated with the tribrach 27.The provision of screws and/or of a spirit level is optional and isintended for improving the safe horizontal alignment. Located at theouter end of the spacer 20 is the retaining part 21 into which a hookmounted in a conventional manner at the end of the scale tape 1 isintroduced. This retaining part comprises two parallel rods 21 a and 21b. The former is optionally rotatably mounted and has a cut-out throughwhich the hook of the roll-type tape measure is passed.

FIG. 3a shows an alternative fastening variant in which a spike 21 a″ isprovided as a retaining part on the spacer 20, by means of which spikethe hook end of the scale tape 1 is fastened with a recess 33.

A variant for a spacer 20′ according to the invention is shown in FIG.4a in elevation and in FIG. 4b in plan view. As described above, it isfastened to the already horizontal tribrach 27, at the cap 19 of theadjusting screw by means of a clamp 24′ provided instead of the hole 24shown in FIG. 3. Two feet 23′ on the underside of the spacer 20′ engagethe tribrach 27 from below, so that the spacer 20′ is fastened in asubstantially firmly clamped manner to the tribrach 27 and ishorizontally positioned. Contact points 34 on the feet 23′ and in theregion of the spacer 20′ resting on the top of the tribrach 27advantageously prevent rotation of the spacer 20′ in the heightdirection. The retaining part 21′ for the hook 8 provided on that end ofthe scale tape 1 which is to be drawn out is present at that end of thespacer 20′ which faces away from the tribrach 27. The geodetic tool 28is indicated in FIG. 4a.

FIG. 4c shows the retaining part 21′ with the hook 8 of the roll-typetape measure 2 already fastened therein. The retaining part 21′comprises a support part 21 a′ on which the hook 8 rests and a fasteningpart 21 b′ which prevents the hook 8 from slipping off the support part21 a′. A slot 21 c′ which is sufficiently wide to permit easy insertionof that end of the scale tape 1 which is to be drawn out is arrangedlaterally between support part 21 a′ and fastening part 21 b′. Thisfacilitates the fastening of the hook 8. In order to fasten the scalesupport, it is inserted into the slot 21 c′. The scale tape 1 is thendrawn downwards so that the hook 8 slides from above into the region ofthe slot 21 c′ until it rests firmly against the support surface. Thehook 8 is thus fixed and the roll-type tape measure can, as seen in FIG.1, be drawn out and positioned for measuring the distance between, forexample, the optical axis of a theodolite and a reference point.

Sections of scales applied to the scale tape 1 are shown in FIGS. 5a and5 b. The scale in FIG. 5a has a nonlinear scale graduation according tothe abovementioned formula. It may be represented as a mirror image toenable it to be read laterally correctly via the prism 3 (FIG. 2 or 2 b)or may be represented in the usual manner for the design having aconventional inspection window. FIG. 5b shows a scale of a differentdesign which likewise results in a reduction in the error in reading.

Owing to the different graduation marks becoming longer with increasingmeasured quantity, error-free reading is ensured even in the case of amirror-image representation and also when only a relatively smallsection of the scale support is visible in the reading region. This isachieved, for example, by graduation marks 44 of different lengths.Thus, for example, the value 0.1 has the shortest graduation mark andthe value 0.9 the longest graduation mark, possibly with the exceptionof the value 0.5. In a similar manner, it should be possible to providea representation in wedge or arrow form 45, as shown in FIG. 5b.

FIG. 6 shows a plumb bar 1′ having one or more—optionally coded—scaleswhich can be read by a reading means in the form of a slide 18,optionally provided with a reading mark 7. At least one of the appliedscales is nonlinear and is calculated according to the abovementionedformula. The lower edge of the plumb bar can be in the form of a pointedstop 10′ in order to ensure the positioning of the bar on the referencepoint and hence to minimize measurement errors. For measurement of theheight, the bar is placed on the reference point and is held against thespacer so that the height are [sic] directly or—in the case of aplurality of scales optionally otherwise to be confused—only using thereading means formed in one of the manners described above.

What is claimed is:
 1. A system for determining a height (h) of ahorizontally aligned geodetic tool (28) having a tool center (30) abovea reference area, which tool (28) is set such that the tool center (30)is situated on a plumb line (32) passing through a reference point ofthe reference area, and which height (h) is the distance between thereference point and the tool center (30) comprising: a spacer (20)having a retaining part (21), which spacer is removably, directly orindirectly fastenable to the tool (28) in such a way that the retainingpart (21) is situated in a predetermined, unalterable, horizontaldistance (b) and a predetermined, unalterable, vertical distance (d) tothe tool center (30); a means for measuring the height (h) by locatingsaid means between the retaining part (21) and the reference point, saidmeans having a nonlinear scale which is designed using the relationshiph=d+{square root over (a²−b²)}, wherein (a) is the distance between theretaining part (21) and the reference point; whereby the height (h) isdeterminable without any calculation, just by reading the nonlinearscale.
 2. The system as claimed in claim 1 wherein the tool (28) ismounted on a horizontally aligned tribrach (27) which is attached to atripod plate (26) of a tripod (25) and wherein the spacer (20) isfastenable to the tribrach (27).
 3. The system as claimed in claim 2,wherein the means for measuring the distance (a) is a roll-type tapemeasure having a measuring spindle (10) at one end for placing on thereference point.
 4. The system as claimed in claim 2, wherein the meansfor measuring the height (h) is a plumb bar (1′) having a stop (10′) atone end for placing on the reference point.
 5. A spacer (20) for asystem for determining the height (h) of a geodetic tool (28) having atool center (30) above a reference area mounted on a horizontallyaligned tribrach (27), which tool (28) is set such that the tool center(30) is situated on a plumb line (32) passing through a reference pointof the reference area, and which height (h) is the distance between thereference point and the tool center (30); which spacer (20) is removablyfastenable to the tribrach (27) and has a retaining part (21) forretaining a means for measuring the height (h) by locating said meansbetween the retaining part (21) and the reference point, said meanshaving a nonlinear scale which is designed using the relationshiph=d+{square root over (a²−b²)}, wherein (a) is the distance between theretaining part (21) and the reference point; and wherein the retainingpart (21) is situated in a predetermined, unalterable, horizontaldistance (b) and in a predetermined, unalterable, vertical distance (d)to the tool center (30) wherein the spacer (20′) comprises a clamp (24′)for gripping a cap (19) of an adjusting screw provided for thehorizontal alignment of the tribrach (27) and two feet (23′) forengaging the underside of the tribrach (27).
 6. A distance measuringdevice for determining a height (h) of a horizontally aligned geodetictool (28) having a tool center (30) above a reference area, which tool(28) is set such that the tool center (30) is situated on a plumb line(32) passing through a reference point of the reference area, wherein aretaining part (21) is attached to the tool (28) in such a way that theretaining part (21) is situated in a predetermined, unalterable,horizontal distance (b) and a predetermined, unalterable, verticaldistance (d) to the tool center (30), which distance measuring devicecomprising: a means for measuring the height (h) by locating said meansbetween the retaining part (21) and the reference point, said meanshaving a nonlinear scale which is designed using the relationshiph=d+{square root over (a²−b²)}, wherein (a) is the distance between theretaining part (21) and the reference point: whereby the height (h) isdeterminable without any calculation, just by reading the nonlinearscale.
 7. The distance measuring device as claimed in claim 6, whereinthe means for measuring the distance comprises a scale support (1, 1′)on which at least one first and one second scale are applied, at leastone of the scales being applied in coded form not directly readable,which scale is indirectly readable by a reading means (3, 18)coordinated with the scale support (1, 1′) and having a reading mark(7).
 8. The distance measuring device as claimed in claim 7, wherein atleast one scale is coded in one of the following ways: the scale isapplied as a mirror image on the scale support; the scale is providedwith a color overprint.
 9. The distance measuring device as claimed inclaim 7, wherein the reading means is formed in one of the followingways: the reading means is in the form of a mirror or prism; the readingmeans is in the form of a color filter.
 10. The distance measuringdevice as claimed in claim 7, wherein at least one of the scales isformed in such a way that each dimension specified numerically iscoordinated with direction information directly indicating the ascendingor descending measured value series, wherein said direction informationis selected from the group consisting of: a graduation mark sequenceincreasing in length, a wedge-shaped mark, and an arrow-shaped mark (23)provided between the dimensions.